1. Field of the Invention
The present invention relates generally to forming a junction or terminus for two ends of glass fibers enabling efficient transmission of light signals thereacross, and, more particularly, to an optical fiber termination of improved reliability and having an expanded beam.
2. Description of Related Art
It is important in the optical fiber field to be able to interconnect the ends of two fibers, or two ends of a fiber that had been broken, for transmitting an optical signal across the junction. A satisfactory connection for this purpose must be able to transmit substantially the entire optical signal and not lose more than a few percent of the signal as it passes through the junction.
One approach to effecting termination of a pair of fibers is that disclosed in U.S. Pat. No. 4,483,584 to John Gresty assigned to the same assignee as the present application. As described in this patent, the ends of the two fibers to be interconnected are faced off to form flat, smooth end surfaces precisely normal to the fiber longitudinal axis. Each of the fibers to be interconnected are mounted within separate sets of three cylindrical pins holding the fiber in the interstices of the pins. Then, the three pins with included fiber are received in opposite ends of a cylindrical alignment tube thereby effecting collimation of the two fibers and locating the ends in slightly spaced, end-facing relation. Although such a connector is effective to transmit light across the junction, it is complex and relatively expensive to manufacture and somewhat difficult to utilize for achieving an optical fiber termination in the field.
In another prior art device disclosed in U.S. Pat. No. 4,290,667, OPTICAL FIBER TERMINATIONS AND CONNECTIONS by Mark Chown, each fiber has its end portion received within a capillary tube with a faced-off fiber end located at the focal point of a lens. A pair of such fiber and lens devices are located in opposite ends of an alignment sleeve to complete the terminus. Other versions in the patent include cladding the optical fiber end within a ball lens either through an appropriately dimensioned opening formed in the lens or through a tapered opening in the lens surface. A still further form shown in this patent locates a fiber within a ferrule and with one end of the ferrule having a central recess for receiving a ball lens therein. In this last version, the fiber end is spaced from the ball lens and a quantity of a clear substance (e.g., epoxy) having refractive index closely matching that of the lens interrelates the lens and fiber.
Although the various approaches depicted in the referenced patent are offered as optical fiber connection means, the practical utilization leaves much to be desired. For example, certain of these constructions are very expensive and complex to manufacture. However, the most serious objection to the devices described is that they are difficult to use in a practical context and quite frequently are not reliable in operation, and as well requires highly trained personnel for fabrication and utilization of the described devices. Also, it is important to note that assembly of such devices must be accomplished in special environments since even extremely small (microscopic size) dust particles if located between fiber ends being terminated will produce a substantial reduction in light transmission efficiency.